Biology Questions

A nitrogenous base, or nitrogen-containing base, is an organic molecule with a nitrogen atom that has the chemical properties of a base. The main biological function of a nitrogenous base is to bond nucleic acids together. A nitrogenous base owes its basic properties to the lone pair of electrons of a nitrogen atom.

In DNA, four bases have been found. They are

1. Adenine (A),

2. Guanine (G),

3. Cytosine (C) and

4. Thymine (T).

The first three of these bases are found in RNA also but the fourth which is Uracil (U) is absent in it.

RNA contains cytosine and uracil as pyrimidine bases while DNA has cytosine and thymine.

Glands are of two types. The exocrine glands have ducts to carry their secretions and these secretions contain enzymes. on the other hand, endocrine glands are ductless glands and they secrete mainly horomones.

Salivary glands of man are 3 pairs = 6. They are one pair of parotid glands, one pair of submaxillary or submandibular glands and one pair of sublingual glands.